1. Field of the Invention
This invention relates to memory integrated circuits and, more particularly, to techniques for electronically interrogating the memory integrated circuit to determine the number of a defective row.
2. Prior Art
Integrated-circuit memories are provided with redundant rows to increase production yield. When a memory row is found to be defective, a redundant row is substituted for the defective row by blowing a fuse associated with that defective row. For Quality Assurance purposes, it is desirable to identify which fuse has been blown in a packaged integrated-circuit device. One way to do this is to etch away enough of the package material with acid to expose all of the fuses and then use a microscope to visually check all of the fuses to see which fuse had been blown, if any. This is a slow and laborious process which limits the amount of data available for statistical analysis.
It is desirable to be able to ascertain which fuse has been blown in a memory integrated-circuit by just electrically interrogating the integrated-circuit, or chip, without having to use acid to etch away some of the material of an integrated-circuit package and without having to visually inspect all of the fuses in the etched part.